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Org. Synth. 1955, 35, 73
DOI: 10.15227/orgsyn.035.0073
HEXAMETHYLBENZENE
[Benzene, hexamethyl-]
Submitted by N. M. Cullinane, S. J. Chard, and C. W. C. Dawkins1.
Checked by T. L. Cairns and D. C. England.
1. Procedure
A solution of 100 g. (1.06 moles) of phenol in 1 l. of methanol is allowed to drop at a rate of 110 ml. per hour (Note 1) over an activated alumina catalyst (Note 2) heated to 530° (Note 3). The exit from the hot tube is attached to a receiver arranged to lead by-product gases to an efficient hood (Note 4). After addition of the methanol solution is finished, the pale yellow product is transferred to a Büchner funnel and washed with methanol. The yield of crude product melting at 135–145° is 112–115 g. (65–67%). Recrystallization from ethanol (50 g. in 650 ml.) gives 85% recovery or from benzene (50 g. in 130 ml.) gives 60% recovery of colorless hexamethylbenzene, m.p. 165–166°.
2. Notes
1. The submitters used a rate of 250 ml. per hour with a 2-in.-diameter tube, 16 in. long, packed with 300 g. of alumina, and a temperature in the catalyst bed about 370–380°. The checkers used 34 g. of alumina packed in a 7/8-in.-diameter tube 13 in. long.
2. The submitters used 4- to 8-mesh alumina from Peter Spence and Sons, Widnes, Lancashire, England. The checkers used 8- to 14-mesh Alorco H-41 obtained from the Aluminum Company of America, 1200 Alcoa Building, Pittsburgh 19, Pennsylvania.
3. Automatically controlling the outside of the catalyst tube to 370–400° gives a hot spot in the catalyst bed of 530° at the rate specified in equipment used by the checkers.
4. Gases formed in the reaction included carbon monoxide, methane, and hydrogen. The exact equation for the reaction is not known.
3. Discussion
Hexamethylbenzene has been prepared by passing the mixed vapors of acetone and methanol over alumina at 400°.2 Briner, Plüss, and Paillard3 have obtained it by passing different phenols mixed with methanol in an atmosphere of dry carbon dioxide over alumina at 410–440°. Hexamethylbenzene also has been prepared by the trimerization of dimethylacetylene in the presence of triethylchromium,4 or a mixture of triisobutylaluminum and titanium tetrachloride.5 The present method is based upon that of Cullinane and Chard.6

References and Notes
  1. University College, Cardiff, Wales.
  2. Reckleben and Scheiber, Ber., 46, 2363 (1913).
  3. Briner, Plüss, and Paillard, Helv. Chim. Acta, 7, 1046 (1924).
  4. Zeiss and Herwig, J. Am. Chem. Soc., 80, 2913 (1958).
  5. Franzus, Canterino, and Wickliffe, J. Am. Chem. Soc., 81, 1514 (1959).
  6. Cullinane and Chard, J. Chem. Soc., 1945, 821.

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

alumina

phenols

activated alumina

ethanol (64-17-5)

Benzene (71-43-2)

methanol (67-56-1)

hydrogen (1333-74-0)

carbon monoxide (630-08-0)

phenol (108-95-2)

carbon dioxide (124-38-9)

acetone (67-64-1)

methane (7782-42-5)

Hexamethylbenzene,
Benzene, hexamethyl- (87-85-4)

titanium tetrachloride (7550-45-0)

dimethylacetylene (503-17-3)

triethylchromium

triisobutylaluminum (100-99-2)